1. Field of the Invention
The present invention relates to a color cathode ray tube, and more particularly to a color cathode ray tube capable of correcting convergence and distortion.
2. Description of the Related Art
With respect to a color cathode ray tube, in general, to make an exterior surface of a panel flat, the visibility of a screen can be improved. However, the flattening of the exterior surface of the panel increases a so-called raster distortion on the screen. Here, the raster distortion is a phenomenon in which the screen cannot hold a rectangular shape and pin distortions appear at upper and lower portions of the screen. In case of a color cathode ray tube having a round exterior panel surface, this raster strain can be made approximately zero. The raster distortion on the screen can be adjusted to some extent by adjusting the wiring distribution of a deflection coil and the magnetization intensity of magnets which are used auxiliary components. Here, the magnets used as the auxiliary components are disposed at positions not away from the horizontal coil wiring adjacent to upper and lower ends of a horizontal deflection coil of the deflection yoke. This is because the deflection yoke is required to be as small as possible to reduce the cost and power consumption. However, with respect to the cathode ray tube having an approximately flat exterior panel surface, there arises a phenomenon that the pin distortion of the screen (hereinafter called xe2x80x9craster distortionxe2x80x9d) cannot be corrected so long as the similar method is used. Accordingly, when it intends to eliminate the raster distortion by the conventional method, it gives rise to a problem that the misconvergence is generated. Here, the convergence means that electron beams which make red, blue and green phosphor elements illuminate are focused on one point on a phosphor screen.
Accordingly, it is an object of the present invention to provide a color cathode ray tube having a flat panel which can cope with the convergence and the raster distortion simultaneously. To achieve this object, irrespective of the shape of a deflection yoke, bar magnets or rod magnets for correcting the raster distortion and the convergence are mounted on the deflection yoke at positions away from an upper end or a lower end of a horizontal deflection coil of the deflection yoke in the direction perpendicular to a tube axis by a distance of not less than 10 mm. Further, not only the magnetization intensity of the magnet but also the magnet length are set to values not less than predetermined values.